Laboratory investigation of GCL hydration from clayey sand subsoil

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The hydration of Geosynthetic Clay Liners (GCLs) from underlying clayey sand subsoil (SC) is studied. The effect of product type and initial subsoil moisture content on GCL hydration is examined for both isothermal conditions at room temperature and for daily thermal cycles over several months. GCL hydration is shown to be highly dependent on the initial moisture content of the subsoil. For a subsoil initial moisture content of 5%, GCLs were only able to reach 12-18% of maximum hydration in over 22 weeks. For a subsoil initial moisture content close to field capacity (20%), GCLs were able to reach 90-91% of maximum hydration over 22 weeks. The method of GCL manufacture is shown to greatly affect the maximum hydration reached as well as the swelling of the respective GCLs. Daily thermal cycles greatly reduced hydration and kept the gravimetric moisture content of the GCLs below 30% of what was reached under isothermal conditions at room temperature. Compared to sand (SP) and silty sand (SM) subsoils, clayey sand (SC) slowed the rate of hydration of the GCLs and reduced the final equilibrium moisture content attained.